Quality of service control in multiple hop wireless communication environments

ABSTRACT

One or more relay stations may be employed along a wireless communication access path between an ingress station and an egress station. A logical communication tunnel is established between the ingress and egress stations through any number of intermediate relay stations to handle session flows of PDUs. As PDUs arrive, the ingress station may determine and add scheduling information to the PDUs before they are delivered to the downstream intermediate relay stations or egress stations. The scheduling information is used by the downstream stations to schedule the PDUs for further delivery. The scheduling information may also be used by the egress station to schedule the PDUs for delivery. The scheduling information added to the PDU by the ingress station bears on a QoS class associated with the PDU, a deadline for the egress station to deliver the PDU, or a combination thereof.

This application claims the benefit of U.S. provisional application Ser.No. 60/949,767 filed Jul. 13, 2007 and U.S. provisional application Ser.No. 61/033,067 filed Mar. 3, 2008, the disclosures of which areincorporated herein by reference in their entireties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to concurrently filed U.S. application Ser.No. 12/172,899, entitled QUALITY OF SERVICE CONTROL IN MULTIPLE HOPWIRELESS COMMUNICATION ENVIRONMENTS, the disclosure of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to wireless communications, and inparticular to controlling quality of service in multiple hop wirelesscommunication environments.

BACKGROUND OF THE INVENTION

Wireless communications have become ubiquitous in modern society.Cellular networks have matured and now provide extensive coverage forvoice communications, and are being increasingly used for data and mediaapplications. However, data rates for cellular networks are relativelylow, and thus are limited to those applications that do not require highdata rates, such as basic Internet browsing, email, text messaging, andlow resolution audio and video streaming. Although such applications areuseful, consumers are demanding richer media experiences that requiresignificantly higher data rates, such as those provided by broadbandservice providers. Broadband access is typically provided by cable andtelephone service providers through hard-wired cable, digital subscriberline (DSL), T1, or T3 connections. Wireless access points may be coupledto the hard-wired connections to provide local wireless zones, orhotspots, in which mobile stations with complementary communicationcapabilities are afforded wireless broadband access.

The Institute for Electrical and Electronics Engineers (IEEE) has setforth a widely used local wireless communication standard, which isreferred to as the IEEE 802.11 standard or Wireless Fidelity standard(WiFi). Unfortunately, a WiFi access point has a very limited range ofat most 100 to 300 feet, depending on environmental conditions. GivenWiFi's limited range, continuous coverage throughout a large geographicarea is impractical, if not impossible. As such, mobile users only getthe benefit of wireless broadband access when they are within a WiFihotspot, which is inherently limited in size.

To address the limitations of WiFi and provide continuous broadbandaccess over much larger areas in a fashion analogous to the coverageprovided by cellular networks, the IEEE has set forth a next generationwireless communication standard, which is referred to as the IEEE 802.16standard or wireless metropolitan area network standard (WiMAN). As theIEEE 802.16 standard has evolved, it has been referred to morefrequently as the Worldwide Interoperability for Microwave Accessstandard (WiMAX). WiMAX promises to extend the wireless broadband accessprovided by a single access point up to 30 miles for fixed stations andthree to ten miles for mobile stations.

Given the extended range provided by WiMAX systems, the access pointsare generally referred to as base stations. Although these base stationsprovide broadband access over much larger areas, environmentalconditions may limit access in certain areas within a given coveragearea. For example, geographic elements, such as hills or valleys, maylimit access within a coverage area. Buildings or other man-madestructures may also affect access throughout a coverage area. Further,access within buildings or mass transit vehicles, such as buses, trains,boats, and the like, may be completely blocked, if not severely limited.

To address these areas of limited access within a coverage area of abase station, one or more relay stations may be employed to effectivelyextend the reach of the base station. Instead of the base stationcommunicating directly with a mobile station or fixed station of an enduser, the relay stations may act as liaisons between these stations andthe base station. One or more relay stations may be provided betweenthese stations and a given base station, depending on the needs of thecommunication environment. The base station and the relay stations usewireless communications to communicate with each other, and the lastrelay station in the relay path will communicate with the mobile orfixed stations. In addition to addressing dead spots in a given coveragearea of a base station, relay stations may also be used to furtherextend the coverage area of a base station. In most instances, relaystations are less complex and expensive than base stations; therefore,using relay stations to extend the coverage area of a single basestation is more economical than installing additional base stations andthe infrastructure needed to connect the base stations to a corecommunication network.

Relay stations may be fixed or mobile. For example, certain relaystations may be permanently affixed to or inside a building, whereasother relay stations may be mounted inside different cars of a subwaytrain. To provide continuous coverage in a coverage area of a given basestation, access provided to a mobile station may be transitioned fromone relay station to another relay station, from the base station to arelay station, or from the base station to a relay station as the mobilestation moves throughout the coverage area of the base station. Accessmay also be transitioned from one base station to another or from arelay station associated with a first base station to a relay stationassociated with a second base station as the mobile station moves fromone location to another. Similarly, moving relay stations may transitionfrom one base station to another as they move from one location toanother.

An issue arising from the use of relay stations is the inability toeffectively control quality of service (QoS) for communications that aresupported, at least in part, through one or more relay stations. QoSgenerally relates to metrics, such as delay, jitter, or data loss, thatimpact the quality of a given communication session or access ingeneral. When a base station communicates directly with a mobile stationover an air interface, it is relatively easy for the base station andthe mobile station to cooperate with one another to both determine thecommunication conditions of the air interface and take steps to ensure agiven level of QoS is maintained. However, the addition of one or morerelay stations in the communication path significantly complicates QoScontrol, because there are two or more air interfaces between the basestation and fixed or mobile stations, which are communicating with therelay stations. To further complicate matters, the conditions of theseair interfaces may change dynamically, especially when moving relaystations are involved.

The IEEE 802.16j standard addresses the use of relay stations and thecontrol of communications over the multiple, wireless communication hopsbetween a base station and a fixed or mobile station through one or morerelay stations. However, IEEE 80.16j has not yet provided an effectiveand efficient way to provide QoS controls when relay stations areinvolved. As such, there is a need for a technique to provide QoScontrol when relay stations are used in wireless communicationenvironments.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, one or more relaystations may be employed along a wireless communication access pathbetween a base station and a user terminal. The relay station directlyserving the user terminal is an access relay station, and any relaystations between the access relay station and the base station areintermediate relay stations. A logical communication tunnel isestablished between the base station and the access relay station andthrough any intermediate relay stations to handle session flows ofpacket data units (PDUs) for downlink or uplink communications. A singletunnel may handle multiple session flows for the same or different userterminals. For downlink communications, the base station is an ingressstation and the access relay station is an egress station of the tunnel.For uplink communications, the access relay station is the ingressstation and the base station is the egress station of the tunnel.

Assuming the tunnel extends through at least one intermediate relaystation, the ingress station will receive PDUs and schedule the PDUs fordelivery to the first intermediate relay station of the tunnel. The PDUsare then delivered as scheduled via the tunnel to the first intermediaterelay station in the tunnel. If the tunnel extends through multipleintermediate relay stations, the first intermediate relay station willreceive the PDUs and schedule the PDUs for delivery to the nextintermediate relay station of the tunnel. The PDUs are then delivered asscheduled via the tunnel to the next intermediate relay station. Thelast intermediate relay station in the tunnel will receive the PDUs andschedule the PDUs for delivery to the egress station of the tunnel. ThePDUs are then delivered as scheduled via the tunnel to the egressstation. If the egress station is an access relay station, the PDUs arescheduled for delivery to the appropriate user terminals and thendelivered as scheduled via the corresponding access connections. If theegress station is a base station, the PDUs are scheduled for deliveryover the core network and then delivered as scheduled.

As noted, the ingress station, egress station, and any intermediaterelay stations may schedule the PDUs for delivery at different hops inthe wireless communication path. This scheduling is preferably done tomaintain appropriate QoS levels for the various session flows. However,the presence of the tunnel makes it difficult for the intermediate relaystations, and in certain cases the egress stations, to properly scheduledelivery of the PDUs, because these nodes do not have access to anyscheduling or QoS related information for the PDUs. In one embodiment ofthe present invention, the ingress station may add schedulinginformation to the PDUs before they are delivered to the intermediaterelay stations or egress stations. The scheduling information is used bythe intermediate relay stations to schedule the PDUs for delivery to thenext intermediate relay station or the egress station, as the case maybe. The scheduling information may also be used by the egress station toschedule the PDUs for delivery to the corresponding user terminals. Theingress station may add the scheduling information to one or moreheaders or sub-headers of the PDU or in the body of each PDU. The PDUsmay be media access control (MAC) or other protocol level PDUs. In oneembodiment, the scheduling information added to the PDU by the ingressstation bears on a QoS class associated with the PDU, a deadline for theegress station to deliver the PDU to the corresponding user terminals,or a combination thereof.

In one embodiment, when a PDU arrives, the ingress station willdetermine the arrival time for a PDU and determine a deadline for theegress station to deliver the PDU to the user terminal for the downlink,or over the core network for the uplink, based on QoS information forthe PDU. The QoS information may relate to the maximum latency, ordelay, allowed for the PDU to reach the egress station. Based on thearrival time and the QoS information, the ingress station will calculatethe deadline for the egress station to deliver the PDU to the userterminal. Next, the ingress station will determine how long it will takethe PDU to reach the egress station through the tunnel and schedule thePDU for delivery to the first intermediate relay station in a mannerensuring that the PDU will reach the egress station prior to thedeadline for the egress station to deliver the PDU to the user terminalfor the downlink, or over the core network for the uplink.

As noted, the ingress station may add the QoS class information, adeadline for the egress station to deliver the PDU, or both to the PDUprior to delivering it to the first intermediate relay station. Uponreceiving the PDU from the ingress station, the intermediate relaystation may access any available QoS information or deadline informationprovided in the PDU. The first intermediate relay station may thendetermine how long it will take the PDU to reach the egress stationthrough the remaining portion of the tunnel and schedule the PDU fordelivery to the next intermediate relay station or the egress station,as the case may be, in a manner ensuring that the PDU will reach theegress station prior to the deadline for the egress station to deliverthe PDU to the user terminal for the downlink, or over the core networkfor the uplink. The PDU may be processed in the same manner by eachintermediate relay station until the PDU reaches the egress station. Theegress station may use the delay information in the PDU for schedulingthe PDU for delivery to the user terminal. The egress station willdeliver the PDU to the user terminal prior to the deadline for theegress station to deliver the PDU to the user terminal for the downlink,or over the core network for the uplink. Notably, the QoS classinformation may be used to break scheduling ties where multiple PDUs arescheduled for delivery by an ingress station, intermediate relaystation, or egress station at the same time. Preferably, the PDUsassociated with a higher class of service are delivered before thosewith a lower class of service. Further, the scheduling or deliverydeadlines may be based on a particular frame or time.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a communication environment according to one embodiment of thepresent invention.

FIG. 2 is a block representation of a wireless communication pathaccording to one embodiment of the present invention.

FIGS. 3A-3C provide a communication flow for downlink communicationsaccording to one embodiment of the present invention.

FIG. 4 is a block representation illustrating the use of a link log inassociation with downlink communications according to one embodiment ofthe present invention.

FIGS. 5A-5C provide a communication flow for uplink communicationsaccording to one embodiment of the present invention.

FIG. 6 is a block representation illustrating the use of a link log inassociation with uplink communications according to one embodiment ofthe present invention.

FIG. 7 is a block representation of a base station according to oneembodiment of the present invention.

FIG. 8 is a block representation of a user terminal according to oneembodiment of the present invention.

FIG. 9 is a block representation of a relay station, such as an accessrelay station or intermediate relay station, according to one embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

With reference to FIG. 1, a wireless communication environment 10 isillustrated according to one embodiment of the present invention. Asdepicted, various user terminals (UT) 12 may communicate over a corenetwork 14 through a corresponding base station controller (BSC) 16,base station (BS) 18, and one or more relay stations. Depending on thelocation and function of the relay stations, the relay stations may beconsidered intermediate relay stations (IR) 20 or access relay stations(AR) 22. The user terminals 12 may represent mobile or fixed terminalsthat are capable of supporting wireless communications with one or moreof the base stations 18 and access relay stations 22. The intermediaterelay stations 20 and access relay stations 22 also support wirelesscommunications. In particular, the access relay stations 22 will supportwireless communications with the user terminals 12 as well as withintermediate relay stations 20 or base stations 18. One or moreintermediate relay stations 20 will reside between a base station 18 andan access relay station 22, and will facilitate wireless communicationswith the base station 18, with the access relay station 22, or both.

Accordingly, a user terminal 12 may communicate directly with a basestation 18 or an access relay station 22. As illustrated, user terminal12A is served directly by a base station 18. User terminals 12B, 12C,and 12D are served by different access relay stations 22. The accessrelay station 22 that serves user terminal 12B is directly served by abase station 18. User terminal 12C is served by an access relay station22 that is linked to a base station 18 through a single intermediaterelay station 20. User terminal 12D is served by an access relay station22 that is coupled to a base station 18 through two intermediate relaystations 20. As such, user terminals 12 may be served by base stations18 or access relay stations 22, and any number of intermediate relaystations 20 may be provided to wirelessly connect a base station 18 witha given access relay station 22.

Preferably, the user terminals 12 are able to move about thecommunication environment 10, and thus be served by different accessrelay stations 22 and base stations 18, depending on their location.Further, the access relay stations 22 may be mobile or fixed.Accordingly, the access relay stations 22 may transition from beingserved directly by one base station 18 to another base station 18, or anintermediate relay station 20. Mobile access relay stations 22 may alsotransition from one intermediate relay station 20 to another.

Communications between the base stations 18, intermediate relay stations20, access relay stations 22, and the user terminals 12 are provided viawireless communication links. Each communication link is considered a“hop.” When a user terminal 12, such as user terminal 12A, is serveddirectly by a base station 18, the access path is considered to be asingle-hop wireless communication path. When one or more relay stationsreside in the access path, the access path is considered a multi-hopwireless communication path. Accordingly, the access path between userterminal 12B and its serving base station 18 is a dual-hop wirelesscommunication path. The access path between user terminal 12C and itsserving base station 18 is considered a three-hop wireless communicationpath, while the access path between user terminal 12D and its servingbase station 18 is considered a four-hop wireless communication path.

For single-hop wireless communication paths, the user terminals 12 andbase stations 18 can communicate with each other and determine thechannel conditions or other factors that may impact the exchange of databetween the two entities. When dealing with only a single wirelesscommunication link, the base station 18 can relatively easily determinethe channel conditions associated with the wireless communication linkand schedule downlink communications to the user terminal 12 and uplinkcommunications from the user terminal 12 to ensure appropriate qualityof service (QoS) levels are maintained. However, when relay stations areemployed, multiple hops, and thus multiple wireless communication links,reside between the base station 18 and the corresponding user terminal12. While the base station 18 may be able to derive an indication of thechannel conditions between it and the relay station with which itdirectly communicates, the channel conditions for wireless communicationlinks between the relay station and the user terminal 12 or other relaystations is not directly accessible by the base station 18. Given theability for certain relay stations and user terminals 12 to move, thesechannel conditions may change dynamically and continuously. As such,scheduling uplink and downlink transmissions in a manner ensuringcertain QoS levels are maintained has proven to be challenging.

In many situations, different user terminals 12 may require differentQoS levels. Further, different types of communications may be associatedwith different QoS levels. For example, different subscribers may paydifferent rates for different overall QoS levels. Further, certain mediaapplications, such as streaming audio and video as well as voice, mayrequire higher QoS levels than certain web browsing or file transferapplications. For the most part, the part of the communication path thatis most likely to change is the wireless access portion residing betweenthe base station 18 and the user terminal 12, either directly or throughone or more relay stations. Accordingly, the present invention employstechniques to take into consideration the impact of the various wirelesscommunication links along the wireless access path, in light of QoSrequirements, to control the scheduling of uplink and downlinkcommunications.

With reference to FIG. 2, one or more relay stations may be employedalong a wireless communication access path between the base station 18and the user terminal 12. Wireless relay links 24 are provided betweenthe base station 18 and the intermediate relay station 20 as well asbetween the intermediate relay station 20 and the access relay station22. A wireless access link 26 provided between the access relay station22 and the user terminal 12. If multiple intermediate relay stations 20are provided in the wireless communication access path, relay links 24are also established between the intermediate relay stations 20. Asnoted, the relay station directly serving the user terminal 12 is anaccess relay station 22, and any relay stations between the access relaystation 22 and the base station 18 are intermediate relay stations 20. Alogical communication tunnel is established between the base station 18and the access relay station 22 and through one or more intermediaterelay stations 20 to handle session flows of PDUs for downlink or uplinkcommunications. This tunnel is referred to as a BS-AR tunnel 28, anddifferent tunnels may be used for uplink and downlink communications.The BS-AR tunnel 28 may handle multiple session flows for the same ordifferent user terminals 12. For downlink communications, the basestation 18 is an ingress station and the access relay station 22 is anegress station of the BS-AR tunnel 28. For uplink communications, theaccess relay station 22 is the ingress station and the base station 18is the egress station of a BS-AR tunnel 28.

Assuming the BS-AR tunnel 28 extends through at least one intermediaterelay station 20 as depicted, the ingress station will receive PDUs andschedule the PDUs for delivery to the first intermediate relay station20 of the tunnel. The PDUs are then delivered as scheduled via the BS-ARtunnel 28 to the first intermediate relay station 20 in the BS-AR tunnel28. If the BS-AR tunnel 28 extends through multiple intermediate relaystations 20 (not shown in FIG. 2), the first intermediate relay station20 will receive the PDUs and schedule the PDUs for delivery to the nextintermediate relay station 20 of the BS-AR tunnel 28. The PDUs are thendelivered as scheduled via the tunnel to the next intermediate relaystation 20. The last intermediate relay station 20 in the BS-AR tunnel28 will receive the PDUs and schedule the PDUs for delivery to theegress station. The PDUs are then delivered as scheduled via the BS-ARtunnel 28 to the egress station. If the egress station is an accessrelay station 22, the PDUs are scheduled for delivery to the appropriateuser terminals 12 and then delivered as scheduled via the correspondingaccess connection 30, which is provided via the access link 26. If theegress station is a base station 18, the PDUs are scheduled for deliveryover the core network 14 and then delivered as scheduled.

As noted, the ingress station, egress station, and any intermediaterelay stations 20 may schedule the PDUs for delivery at different hopsin the wireless communication path. This scheduling is preferably doneto maintain appropriate QoS levels for the various session flows.However, the presence of the BS-AR tunnel 28 makes it difficult for theintermediate relay stations 20, and in certain cases the egressstations, to properly schedule delivery of the PDUs because these nodesdo not normally have access to any scheduling or QoS related informationfor the PDUs. In one embodiment of the present invention, the ingressstation may add scheduling information to the PDUs before they aredelivered to the intermediate relay stations 20 or egress station. Thescheduling information is used by the intermediate relay stations 20 toschedule the PDUs for delivery to the next intermediate relay station 20or the egress station, as the case may be. The scheduling informationmay also be used by the egress station to schedule the PDUs for deliveryto the corresponding user terminals 12. The ingress station may add thescheduling information to a header or in the body of each PDU. In oneembodiment, the scheduling information added to the PDU by the ingressstation bears on a QoS class associated with the PDU, a deadline for theegress station to deliver the PDU to the corresponding user terminals 12for the downlink, or over the core network 14 for the uplink, or acombination thereof.

When a PDU arrives, the ingress station will determine the arrival timefor a PDU and determine a deadline for the egress station to deliver thePDU to the user terminal 12 for the downlink, or over the core network14 for the uplink, based on QoS information for the PDU. The QoSinformation may relate to the maximum latency, or delay, allowed for thePDU to reach the egress station. Based on the arrival time and the QoSinformation, the ingress station will calculate the deadline for theegress station to deliver the PDU to the user terminal 12 for thedownlink, or over the core network 14 for the uplink. Next, the ingressstation will determine how long it will take the PDU to reach the egressstation through the tunnel and schedule the PDU for delivery to thefirst intermediate relay station 20 in a manner ensuring that the PDUwill reach the egress station prior to the deadline for the egressstation to deliver the PDU to the user terminal 12 for the downlink, orover the core network 14 for the downlink.

As noted, the ingress station may add the QoS class information, adeadline for the egress station to deliver the PDU to the user terminal12 for the downlink or over the core network 14 for the uplink, or both,to the PDU prior to delivering it to the first (and only illustrated)intermediate relay station 20. Upon receiving the PDU from the ingressstation, the first intermediate relay station 20 may access anyavailable QoS information or deadline information provided in the PDU.The first intermediate relay station 20 may then determine how long itwill take the PDU to reach the egress station through the remainingportion of the tunnel and schedule the PDU for delivery to the nextintermediate relay station 20 (not illustrated) or the egress station(as illustrated), as the case may be, in a manner ensuring that the PDUwill reach the egress station prior to the deadline for the egressstation to deliver the PDU to the user terminal 12 for the downlink, orover the core network 14 for the uplink. The PDU may be processed in thesame manner by each intermediate relay station 20 until the PDU reachesthe egress station. The egress station may use the delay information inthe PDU for scheduling the PDU for delivery to the user terminal 12 forthe downlink or over the core network 14 for the uplink. The egressstation will deliver the PDU prior to the deadline for the egressstation to the deliver the PDU to the user terminal 12 for the downlink,or over the core network 14 for the uplink. Notably, the QoS classinformation may be used to break scheduling ties where multiple PDUs arescheduled for delivery by an ingress station, intermediate relay station20, or egress station at the same time. Preferably, the PDUs associatedwith a higher class of service are delivered before those with a lowerclass of service. Further, the scheduling or delivery deadlines may bebased on a particular frame or time.

With reference to FIGS. 3A-3C, a communication flow is providedaccording to one embodiment of the present invention to illustrate anexemplary scheduling process for downlink communications. In thisexample, assume the wireless communication access path is the same orsimilar to that illustrated in FIG. 2. The communication flowillustrates the handling of a given PDU that is received from the corenetwork 14 through the base station controller 16. Initially, anincoming PDU is received and then processed by the base station 18(steps 100 and 102). The base station 18 will note the time at which thePDU arrives at the base station 18, and will store information relatedto the arrival time as the base station arrival time (t_(BSA)) (step104).

As indicated, the PDU is one of a number of PDUs that make up a sessionflow for a given communication session. A service flow may be assignedto one of any number of defined QoS classes. Each class will beassociated with various QoS parameters that should control how PDUs forthe given session flow are handled for uplink or downlinkcommunications. The QoS parameters are maintained in a QoS profile forthe particular QoS class. In one embodiment, the QoS parameters providedin the QoS class define latency information, which relates to themaximum delay between the base station arrival time t_(BSA) and anaccess link delivery deadline (t_(ADL)), which corresponds to a time ator before which the PDU should be transmitted directly to the userterminal 12 over the access link 26.

Notably, when a session flow is established, a service node in the corenetwork 14 will assign a QoS class for the service flow. The servicenode may provide the base station 18 with class identificationinformation for the service flow, wherein the base station 18 will beable to analyze information provided in a PDU and identify the QoS classfor the service flow to which the PDU belongs. When the service flow isbeing established, the base station 18 may access the corresponding QoSprofile for the corresponding QoS class identification information.Thus, the base station 18 may gather information from the PDU todetermine the service flow to which the PDU belongs, and then determinethe QoS class for the service flow. Alternatively, the PDU may includeinformation related to the appropriate QoS class, and the base station18 may identify the appropriate QoS class based on the informationprovided in the PDU itself.

Regardless of the technique, the base station 18 will identify QoS classinformation for the PDU (step 106) and access the QoS profile for thePDU based on the class information (step 108). From the QoS profile, thebase station 18 may obtain the latency information (t_(LAT)) from theQoS profile (step 110). Based on the base station arrival time (t_(BSA))and the latency information (t_(LAT)), the base station 18 may determinean access link delivery deadline (t_(ADL)) (step 112). The access linkdelivery deadline t_(ADL) corresponds to the latest time or frame atwhich the PDU can be delivered to the user terminal 12 from the accessrelay station 22. If the latency information t_(LAT) corresponds tomaximum allowable time from which the PDU arrived at the base station 18and the time from which the PDU should be transmitted from the accessrelay station 22, the access link delivery deadline t_(ADL) can becalculated by adding the latency information t_(LAT) to the base stationarrival time t_(BSA), wherein t_(ADL)=t_(BSA)+t_(LAT).

At this point, the base station 18 is aware of the latest time or frameat which the PDU should be transmitted from the access relay station 22.However, there are two relay links 24 that reside between the basestation 18 and the access relay station 22. Accordingly, in order forthe base station 18 to ensure that the PDU arrives at the access relaystation 22 in time to be transmitted to the user terminal 12 by theaccess link delivery deadline t_(ADL), the base station 18 needs toensure that the PDU is transmitted to the intermediate relay station 20in sufficient time to allow the intermediate relay station 20 to deliverthe PDU to the access relay station 22 prior to the access link deliverydeadline t_(ADL). Accordingly, the base station 18 will calculate afirst relay link delivery deadline (t_(RDL1)) based on the access linkdelivery deadline T_(ADL) and BS-AR propagation information (t_(BS-AR))(step 114). The first relay link delivery deadline t_(RDL1) correspondsto the last time or frame at which the PDU can be transmitted to theintermediate relay station 20 by the base station 18 and still maintainthe desired QoS level. The BS-AR propagation information t_(BS-AR)corresponds to a time it takes for a PDU that is transmitted from thebase station 18 to propagate to the access relay station 22 through therelay links 24 and the intermediate relay station 20. Accordingly, theBS-AR propagation information t_(BS-AR) corresponds to the time it takesa PDU to pass through the BS-AR tunnel 28, which extends between thebase station 18 and the access relay station 22. In this example, thefirst relay link delivery deadline t_(RDL1) may be determined bysubtracting the BS-AR propagation information t_(BS-AR) from the accesslink delivery deadline t_(ADL), wherein t_(RDL1)=t_(ADL)−t_(BS-AR).

At this point, the base station 18 knows the last time or frame at whichthe PDU can be transmitted to the intermediate relay station 20 andstill meet QoS requirements. Since the base station 18 will be handlingmultiple PDUs for multiple session flows, the base station 18 will beproviding these steps for each PDU and determining when to transmit thevarious PDUs toward the various intermediate relay stations 20, accessrelay stations 22, or user terminals 12, depending on the number of hopsin the wireless communication path. In one embodiment, each PDU isscheduled to be transmitted at a particular time or in a particularframe based on the first relay link delivery deadline t_(RDL1).

Prior to transmission of the PDU to the intermediate relay station 20,the base station 18 will attach QoS class information and the accesslink delivery deadline t_(ADL) to the PDU in one or more headers orsub-headers or in the actual body of the information being carried inthe PDU (step 116). In a preferred embodiment, the QoS class informationand access link delivery deadline is provided in the same or differentsub-headers in a media access control (MAC) PDU. By providing the QoSclass information and the access link delivery deadline t_(ADL) in thePDU, the intermediate relay station 20 is able to identify the QoS classassociated with the PDU and use the access link delivery deadlinet_(ADL) to determine when the PDU should be transmitted to the accessrelay station 22 in order to maintain the desired level of QoS.Accordingly, the base station 18 will transmit the PDU to theintermediate relay station 20 on or before the first link deliverydeadline t_(RDL1) (step 118). Notably, if multiple PDUs for differentsession flows have the same first link delivery deadline t_(RDL1), thebase station 18 may use the QoS class information to break ties amongthe PDU delivery times. Those PDUs associated with a higher QoS classwill be transmitted to the appropriate intermediate relay station 20 (orother appropriate relay station or user terminal) before PDUs associatedwith a lower QoS class.

Next, the intermediate relay station 20 will receive the PDU, whichincludes the QoS class information as well as the access link deliverydeadline t_(ADL) (step 120). The intermediate relay station 20 will thencalculate a second relay link delivery deadline (t_(RDL2)) based on theaccess link delivery deadline t_(ADL) and IR-AR propagation information(t_(IR-AR)) (step 122). The second relay link delivery deadline t_(RDL2)corresponds to the latest time or frame at which the PDU should betransmitted to the access relay station 22 in order to maintain therequired QoS level. For instance, the second relay link deliverydeadline t_(RDL2) may be calculated by subtracting the IR-AR propagationinformation t_(IR-AR) from the access link delivery deadline t_(ADL),wherein: t_(RDL2)=t_(ADL)−t_(IR-AR).

The intermediate relay station will then transmit the PDU to the accessrelay station 22 on or before the second relay link delivery deadlinet_(RDL2) (step 124). Again, the QoS class information for the variousPDUs may be used to break ties for PDUs that have the same relay linkdelivery deadline. Notably, the PDU will be delivered to the accessrelay station 22 with the QoS class information as well as the accesslink delivery deadline t_(ADL) (step 126). The access relay station 22will transmit the PDU to the user terminal 12 on or before the accesslink delivery deadline t_(ADL) (step 128). The access relay station 22may break ties for PDUs that have the same access link deliverydeadlines based on the QoS class associated with the respective PDUs.The PDU may be delivered to the user terminal 12 over the access link 26and the appropriate access connection 30, with or without the QoS classinformation or the access link delivery deadline (step 130).

As noted above, the BS-AR propagation information, t_(BS-AR), bears onthe amount of time a PDU takes to travel to the access relay station 22from the base station 18; however, it does not have to be measured inunits of time. For scheduling delivery of the PDU to the intermediaterelay station 20, the base station 18 uses the BS-AR propagationinformation, t_(BS-AR), to calculate the first relay link deliverydeadline. The BS-AR propagation information, t_(BS-AR), may bedetermined in a variety of ways using different types of information.For example, each hop between the base station 18 and the access relaystation 22 may be associated with a normalized delivery time, t_(norm)and the BS-AR propagation information, t_(BS-AR), may simply be based onthe number of hops, n, between the base station 18 and the access relaystation 22 in light of the normalized delivery time, t_(norm) for thevarious hops. Accordingly, the BS-AR propagation information, t_(BS-AR),may be determined as follows:t _(BS-AR) =n*t _(norm)  Eq. 1

If actual or average delivery times are available for each hop, theBS-AR propagation information t_(BS-AR), may be based on these deliverytimes. Using the example above, the BS-AR propagation informationt_(BS-AR) may be determined as follows:t _(BS-AR) =t _(hop1) +t _(hop2)  Eq. 2where t_(hop1) represents the actual or average delivery time for PDUsbeing delivered from the base station 18 to the intermediate relaystation 20 and t_(hop2) represents the actual or average delivery timefor PDUs being delivered from the intermediate relay station 20 to theaccess relay station 22.

Similarly, the IR-AR propagation information, t_(IR-AR), bears on theamount of time it should take a PDU to travel to the access relaystation 22 from the intermediate relay station 20. For schedulingdelivery of the PDU to the access relay station 22, the intermediaterelay station 20 uses the IR-AR propagation information t_(IR-AR) tocalculate the second relay link delivery deadline t_(RDL2). The IR-ARpropagation information t_(IR-AR) may be determined in a similar fashionas the BS-AR propagation information t_(BS-AR). For example, eachremaining hop between the intermediate relay station 20 and the accessrelay station 22 may be associated with a normalized delivery timet_(norm) and the BS-AR propagation information t_(BS-AR) may simply bebased on the number of remaining hops, m, between the base station 18and the access relay station 22 in light of the normalized delivery timet_(norm) for the remaining hops. Accordingly, the BS-AR propagationinformation t_(BS-AR) may be determined as follows:t _(BS-AR) =m*t _(norm)  Eq. 3

If actual or average delivery times are available for the remaining hop(or hops), the IR-AR propagation information t_(IR-AR) may be based onthese delivery times. Using the example above, the IR-AR propagationinformation t_(IR-AR), may be determined as follows:T _(IR-AR) =t _(hop2)  Eq. 4where t_(hop2) again represents the actual or average delivery time forPDUs being delivered from the intermediate relay station 20 to theaccess relay station 22.

The BS-AR and IR-AR propagation information may be obtained by the basestation 18 or the intermediate relay station 20 in a variety of ways.For normalized information, the respective stations may have access tothe number of hops to the access relay station 22 and use standardizedhop times for the corresponding calculations. In more complexembodiments, link performance information based on actual or average hoptimes may be exchanged between the various stations. For example, theaccess relay station 22 may monitor access link metrics for the accesslink 26 and report the access link metrics to the intermediate relaystation 20. The intermediate relay station 20 may monitor relay linkmetrics for the relay link 24, which resides between the intermediaterelay station 20 and the access relay station 22. Based on the relaylink metrics, the intermediate relay station 20 can determine a hop timefor the relay link 24, which resides between the access relay station 22and the intermediate relay station 20. As such, the relay link metricsfor the relay link 24 between the intermediate relay station 20 and theaccess relay station 22 may represent or be used to determine the BS-ARpropagation information t_(IR-AR).

The intermediate relay station 20 may also provide the relay linkmetrics for the relay link 24 between the intermediate relay station 20and the access relay station 22 along with the access link metrics tothe base station 18. The base station 18 may monitor relay link metricsfor the relay link 24 residing between the intermediate relay station 20and the base station 18, and determine a hop time for the relay link 24residing between the base station 18 and the intermediate relay station20. As noted, the base station 18 receives relay link metrics from theintermediate relays station 20 for the relay link 24 between theintermediate relay station 20 and the access relay station 22. As such,the base station 18 has relay link metrics for both relay links 24 thatreside between the base station 18 and the access relay station 22. Therelay link metrics for these relay links 24 may represent or be used todetermine the BS-AR propagation information t_(BS-AR).

The BS-AR and IR-AR propagation information may take various forms andbe derived from different types of relay link metrics. For example, therelay link metrics for a given relay link may represent an aggregate ofthe transmission times, delays, or throughput over the link for PDUsthat belong to a given QoS class regardless of their destination, forPDUs being sent to or from a given user terminal 12, for PDUs that areassociated with a given service flow, for PDUs that are associated witha given type of service flow, or the like. The relay link metrics formultiple relay links 24 may be further aggregated to determinenormalized link metrics for some or all of the relay links 24 along theBS-AR tunnel 28.

With reference to FIG. 4, a link log LL for downlink session flows maybe used to deliver the link metrics from one station to another. Therelay link metrics may represent, correspond to, or be used to derivethe BS-AR propagation information or IR-AR propagation information,which were used for scheduling as described in association with exampleprovided in FIGS. 3A-3C. The link log LL may be configured as a templatewith fields that can be populated by the different stations for thedifferent link metrics. For downlink session flows, the access linkmetrics (AR-UT) may be provided in a first field of the link log LL bythe access relay station 22. The access relay station 22 will forwardthe link log LL to the intermediate relay station 20. The relay linkmetrics for the relay link 24 between the intermediate relay station 20and the access relay station 22 (IR-AR) may be provided in a secondfield in the link log LL by the intermediate relay station 20. Theintermediate relay station 20 will forward the populated link log LL tothe base station 18, wherein the link log LL may have the access linkmetrics (AR-UT) as well as the relay link metrics (IR-AR) for the relaylink 24 that resides between the intermediate relay station 20 and theaccess relay station 22. As indicated, the base station 18 may monitorthe relay link metrics for the relay link 24 that resides between theintermediate relay station 20 and the base station 18 (BS-IR).Accordingly, the base station 18 will have access to the relay linkmetrics for each of the relay links 24 between the base station 18 andthe access relay station 22. The link log LL will support any number ofintermediate relay stations 20.

For the communication flow described in association with FIGS. 3A-3C,the base station 18 was the ingress station, while the access relaystation 22 was the egress station, and as such, PDUs flowed from thebase station 18 to the access relay station 22 through the BS-AR tunnel28. The present invention is equally applicable for uplinkcommunications, wherein the access relay station 22 is the ingressstation and the base station 18 is the egress station. As such, PDUs aredelivered from the access relay station 22 to the base station 18through one or more intermediate relay stations 20 via an AR-BS tunnel.The AR-BS tunnel is not shown, but is similar to the BS-AR tunnel 28.The reversal of the nomenclature, BS-AR to AR-BS, signifies thedirection of service flow. An example of how the present inventionapplied to uplink communications is provided in the communication flowof FIGS. 5A-5C.

For a given service flow, the access relay station 22 may obtain thecorresponding QoS class information or the QoS profile from the basestation 18 through the intermediate relay station 20 (steps 200 and202). This information may be provided directly by the base station 18or retrieved from another service node by the access relay station 22based on information received from the base station 18. The access relaystation 22 may identify the latency information t_(LAT) from the QoSprofile (step 204). As described above, the latency information t_(LAT)corresponds to the maximum amount of time allowed for a PDU to travelfrom the access relay station 22 to the base station 18 through theAR-BS tunnel. When a PDU for the corresponding service flow is receivedby the access relay station 22 from the user terminal 12 (step 206), theaccess relay station 22 will identify and store the access relay stationarrival time (t_(ARA)) (step 208). The access relay station 22 will thendetermine the network delivery deadline (t_(NDL)) based on the accessrelay station arrival time t_(ARA) and the latency information t_(LAT)(step 210). The network delivery deadline t_(NDL) represents the time orframe at or before which the PDU must be delivered over the core network14 by the base station 18. For example, the network delivery deadlinet_(NDL) may be calculated by adding the latency information t_(LAT) tothe access relay station arrival time t_(ARA), whereint_(NDL)=t_(ARA)+t_(LAT).

At this point, the access relay station 22 knows when the PDU must bedelivered by the base station 18 over the core network 14. The accessrelay station 22 must next take steps to ensure the PDU is delivered tothe base station 18 prior to the network delivery deadline t_(NDL). Inone embodiment, the access relay station 22 will calculate a secondrelay link delivery deadline (t_(RDL2)) based on the network delivertime t_(NDL) and AR-BS propagation information (t_(AR-BS)) (step 212).The second relay link delivery deadline t_(RDL2) represents the time orframe on or before which the PDU should be delivered to the intermediaterelay station 20 over the second relay link 24. The AR-BS propagationinformation t_(AR-BS) corresponds to an amount of time it takes a PDU totravel from the access relay station 22 to the base station 18 via theAR-BS tunnel. In this example, the second relay link delivery deadlinet_(RDL2) is calculated by subtracting the AR-BS propagation informationt_(AR-BS) from the network delivery deadline t_(NDL), whereint_(RDL2)=t_(NDL)−t_(AR-BS).

At this point, the access relay station 22 knows the latest time orframe at which the PDU should be delivered to the intermediate relaystation 20. Prior to delivering the PDU to the intermediate relaystation 20, the access relay station 22 will attach the QoS classinformation and the network delivery deadline t_(NDL) in a header orbody of the PDU (step 214). The access relay station 22 will thentransmit the PDU to the intermediate relay station 20 on or before thesecond relay link delivery deadline t_(RDL2) (step 216). In a preferredembodiment, the QoS class information and network link delivery deadlineis provided in the same or different sub-headers in a MAC PDU; however,the information may be delivered with the PDU in any manner. If multiplePDUs from the same or different user terminals 12 end up having the samesecond relay link delivery deadline t_(RDL2), the QoS class informationassociated with the PDUs may be used to break ties among the PDUdelivery times. Accordingly, the PDU is delivered to the intermediaterelay station 20 and will include the QoS class information and thenetwork delivery deadline t_(NDL) (step 218).

At this point, the intermediate relay station 20 must schedule the PDUfor delivery to the base station 18, such that the PDU is delivered tothe base station 18 in sufficient time for the base station 18 todeliver the PDU over the core network 14 prior to the network deliverydeadline t_(NDL). Accordingly, the intermediate relay station 20 willcalculate a first relay link delivery deadline (t_(RDL1)) based on thenetwork delivery deadline t_(NDL) and IR-BS propagation information(t_(IR-BS)) (step 220). The intermediate relay station 20 may recoverthe network delivery deadline t_(NDL) from the PDU. The IR-BSpropagation information t_(IR-BS) relates to the amount of time it takesa PDU to travel from the intermediate relay station 20 to the basestation 18 through the remaining portion of the AR-BS tunnel. In thisexample, assume the first relay link delivery deadline t_(RDL1) iscalculated by subtracting the IR-BS propagation information t_(IR-BS)from the network delivery deadline t_(NDL), whereint_(RDL1)=t_(NDL)−t_(IR-BS).

At this point, the intermediate relay station 20 knows to schedule thePDU for delivery to the base station 18 on or before the first relaylink delivery deadline t_(RDL1). Again, delivery deadlines maycorrespond to times or frames at or before which a PDU must bedelivered. Accordingly, the intermediate relay station 20 will transmitthe PDU to the base station 18 on or before the first relay linkdelivery deadline t_(RDL1) (step 222). Again, the QoS class informationthat is provided in the PDU by the access relay station 22 may be usedto break ties among PDU delivery times. The PDU is delivered to the basestation 18 and will include the QoS class information as well as thenetwork delivery deadline t_(NDL) (step 224). The base station 18 willtransmit the PDU over the core network 14 on or before the networkdelivery deadline t_(NDL) provided in the PDU (step 226). Again, the QoSclass information provided in the PDU or otherwise known by the basestation 18 may be used to break ties among the PDU delivery times. Assuch, the base station 18 will deliver the PDU over the core network 14(step 228).

With reference to FIG. 6, a link log LL for uplink session flows may beused to deliver the link metrics from one station to another. The relaylink metrics may represent, correspond to, or be used to derive theAR-BS propagation information or IR-BS propagation information, whichwere used for scheduling as described in association with exampleprovided in FIGS. 5A-5C. As for the link log LL for downlink sessionflows, the uplink link log LL may be configured as a template withfields that can be populated by the different stations for the differentlink metrics. For uplink session flows according to the illustratedexamples, the relay link metrics for the relay link 24 between theintermediate relay station 20 and the base station 18 (IR-BS) may beprovided in a first field of the link log LL by the intermediate relaystation 18. The intermediate relay station 20 may forward the populatedlink log LL to the access relay station 22, wherein the link log LL willhave the relay link metrics for the relay link 24 that resides betweenthe intermediate relay station 20 and the base station 18 (IR-BS). Theaccess relay station 22 may monitor the relay link metrics for the relaylink 24 that resides between the intermediate relay station 20 and theaccess relay station 22 (IR-AR). Accordingly, the access relay station22 will have access to the relay link metrics for each of the relaylinks 24 between the access relay station 22 and the base station 18.The link log LL will support any number of intermediate relay stations20.

High level overviews of a base station 18, user terminal 12, and a relaystation, such as the intermediate relay station 20 or access relaystation 22, are provided below in association with FIGS. 7, 8, and 9.With particular reference to FIG. 7, a base station 18 configuredaccording to one embodiment of the present invention is illustrated. Thebase station 18 generally includes a control system 32, a basebandprocessor 34, transmit circuitry 36, receive circuitry 38, one moreantennas 40, and a network interface 42. The receive circuitry 38receives radio frequency signals bearing information from one or moreremote transmitters provided by user terminals 12, intermediate relaystations 20, or access relay stations 22. Preferably, a low noiseamplifier and a filter (not shown) cooperate to amplify and removebroadband interference from the signal for processing. Downconversionand digitization circuitry (not shown) will then downconvert thefiltered, received signal to an intermediate or baseband frequencysignal, which is then digitized into one or more digital streams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 34 is generallyimplemented in one or more digital signal processors (DSPs). Thereceived information is then sent toward the core network 14 via thenetwork interface 42 or transmitted toward another user terminal 12serviced by the base station 18. The network interface 42 will typicallyinteract with the core network 14 via the base station controller 16.

On the transmit side, the baseband processor 34 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 42 under the control of control system 32, whichencodes the data for transmission. The encoded data is output to thetransmit circuitry 36, where it is used by a modulator to modulate acarrier signal that is at a desired transmit frequency or frequencies. Apower amplifier (not shown) will amplify the modulated carrier signal toa level appropriate for transmission, and deliver the modulated carriersignal to one or more of the antennas 40 through a matching network.

With reference to FIG. 8, a fixed or mobile user terminal 12 configuredaccording to one embodiment of the present invention is illustrated. Theuser terminal 12 will include a control system 44, a baseband processor46, transmit circuitry 48, receive circuitry 50, one or more antennas52, and a user interface circuitry 54. The receive circuitry 50 receivesradio frequency signals bearing information from one or more remotetransmitters provided by base stations 18 or access relay stations 22.Preferably, a low noise amplifier and a filter (not shown) cooperate toamplify and remove broadband interference from the signal forprocessing. Downconversion and digitization circuitry (not shown) willthen downconvert the filtered, received signal to an intermediate orbaseband frequency signal, which is then digitized into one or moredigital streams. The baseband processor 46 processes the digitizedreceived signal to extract the information or data bits conveyed in thereceived signal. This processing typically comprises demodulation,decoding, and error correction operations. The baseband processor 46 isgenerally implemented in one or more digital signal processors (DSPs).

For transmission, the baseband processor 46 receives digitized data,which may represent voice, data, or control information, from thecontrol system 44, which it encodes for transmission. The encoded datais output to the transmit circuitry 48, where it is used by a modulatorto modulate a carrier signal that is at a desired transmit frequency orfrequencies. A power amplifier (not shown) will amplify the modulatedcarrier signal to a level appropriate for transmission, and deliver themodulated carrier signal to the one or more antennas 52 through amatching network. Various modulation and processing techniques availableto those skilled in the art are applicable to the present invention.

With reference to FIG. 9, a relay station 56 configured according to oneembodiment of the present invention is illustrated. The relay stationmay represent an intermediate relay station 20 or an access relaystation 22. The relay station 56 generally includes a control system 58,a baseband processor 60, transmit circuitry 62, receive circuitry 64,and one more antennas 66. The receive circuitry 64 receives radiofrequency signals bearing information from one or more remotetransmitters provided by user terminals 12, other intermediate relaystations 20, access relay stations 22, or base stations 18. Preferably,a low noise amplifier and a filter (not shown) cooperate to amplify andremove broadband interference from the signal for processing.Downconversion and digitization circuitry (not shown) will thendownconvert the filtered, received signal to an intermediate or basebandfrequency signal, which is then digitized into one or more digitalstreams.

The baseband processor 60 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 60 is generallyimplemented in one or more digital signal processors (DSPs). Thereceived information is then sent toward transmitted toward a userterminal 12, intermediate relay station 20, access relay station 22, orbase station 18 as described below.

On the transmit side, the baseband processor 60 receives digitized data,which may represent voice, data, or control information fortransmission. The digitized data is encoded, and the encoded data isoutput to the transmit circuitry 62, where it is used by a modulator tomodulate a carrier signal that is at a desired transmit frequency orfrequencies. A power amplifier (not shown) will amplify the modulatedcarrier signal to a level appropriate for transmission, and deliver themodulated carrier signal to one or more of the antennas 66 through amatching network.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present invention. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

1. An ingress station that resides in a wireless communication accesspath in a wireless communication environment, wherein a tunnel isestablished with an egress station through one or more intermediaterelay stations along the wireless communication access path, the ingressstation comprising: wireless communication circuitry; a control systemassociated with the wireless communication circuitry and adapted to:receive a plurality of packet data units associated with at least oneservice flow that is supported by the tunnel; for each packet data unitof the plurality of packet data units: determine an egress stationdelivery deadline on or before which the egress station should deliverthe packet data unit toward a destination of the packet data unit;provide the egress station delivery deadline with the packet data unit;and deliver the packet data unit with the egress station deliverydeadline to an intermediate relay station of the one or more relaystations via the tunnel.
 2. The ingress station of claim 1 wherein thecontrol system is further adapted to determine an ingress stationdelivery deadline for the packet data unit on or before which theingress station should deliver the packet data unit to the intermediaterelay station to ensure the packet data unit reaches the egress stationin sufficient time to be delivered toward the destination of the packetdata unit by the egress station delivery deadline.
 3. The ingressstation of claim 2 wherein to determine the ingress station deliverydeadline for the packet data unit, the control system is further adaptedto: determine propagation information bearing on how long it may takethe packet data unit to be delivered to the egress station through theone or more intermediate relay stations; and calculate the ingressstation delivery deadline based on the propagation information and theegress station delivery deadline.
 4. The ingress station of claim 3wherein the ingress station delivery time is calculated at least in partby subtracting the propagation information from the egress stationdelivery deadline.
 5. The ingress station of claim 3 wherein the controlsystem is further adapted to receive propagation metrics bearing on atleast one link between the ingress station and the egress station andwherein the control system determines the propagation information basedon the propagation metrics.
 6. The ingress station of claim 5 whereinthe propagation metrics bear on a link between the intermediate relaystation and the egress station.
 7. The ingress station of claim 5wherein the propagation metrics for the at least one link is provided bythe intermediate relay station in a log, which has a different field forthe propagation metrics for each link being reported.
 8. The ingressstation of claim 2 wherein the control system is further adapted todeliver the packet data unit with the egress station delivery deadlineto the intermediate relay station via the tunnel on or before theingress station delivery deadline.
 9. The ingress station of claim 2wherein when multiple packet data units of the plurality of packet dataunits have the same ingress station delivery deadline, quality ofservice class information associated with the multiple packet data unitsis used to control an order in which the multiple packet data units aredelivered to the intermediate relay station.
 10. The ingress station ofclaim 1 wherein to determine the egress station delivery deadline forthe packet data unit, the control system is further adapted to:determine arrival time information bearing on when the packet data unitwas received at the ingress station; determine latency informationbearing on an acceptable delay before the egress station should deliverthe packet data unit toward a destination of the packet data unit basedon quality of service class information associated with the packet dataunit; and calculate the egress station delivery time for the packet dataunit based on the arrival time information and the latency information.11. The ingress station of claim 10 wherein the egress station deliverytime is determined at least in part by adding the latency information tothe arrival time information for the packet data unit.
 12. The ingressstation of claim 1 wherein the egress station delivery deadlinecorresponds to a time.
 13. The ingress station of claim 1 wherein theegress station delivery deadline corresponds to a frame fortransmission.
 14. The ingress station of claim 1 wherein the ingressstation is a base station and the egress station is an access relaystation supporting wireless communications with at least one userterminal, which is party to the at least one service flow.
 15. Theingress station of claim 1 wherein the egress station is a base stationand the ingress station is an access relay station supporting wirelesscommunications with at least one user terminal, which is party to the atleast one service flow.
 16. The ingress station of claim 1 wherein thecontrol system is further adapted to: identify quality of service (QoS)class information bearing on a QoS class for the packet data unit; andprovide the egress station delivery deadline with the packet data unit,wherein the packet data unit is delivered with the QoS class informationand the egress station delivery deadline to the intermediate relaystation of the one or more relay stations via the tunnel.
 17. Anintermediate relay station that resides in a wireless communicationaccess path in a wireless communication environment, wherein a tunnel isestablished between an ingress station and an egress station through theintermediate relay station along the wireless communication access path,the intermediate relay station comprising: wireless communicationcircuitry; a control system associated with the wireless communicationcircuitry and adapted to: receive a plurality of packet data unitsassociated with at least one service flow that is supported by thetunnel, wherein each of the plurality of packet data units comprises anegress station delivery deadline on or before which the egress stationshould deliver the packet data unit toward a destination of the packetdata unit; and for each packet data unit of the plurality of packet dataunits; determine an intermediate relay station delivery deadline for thepacket data unit on or before which the intermediate relay stationshould deliver the packet data unit toward the egress station to ensurethe packet data unit reaches the egress station in sufficient time to bedelivered toward the destination of the packet data unit by the egressstation delivery deadline; and deliver the packet data unit with theegress station delivery deadline toward the egress station on or beforethe intermediate relay station delivery deadline.
 18. The intermediaterelay station of claim 17 wherein the packet data unit is delivered toanother intermediate relay station that resides between the intermediaterelay station and the egress station.
 19. The intermediate relay stationof claim 17 wherein the packet data unit is received from anotherintermediate relay station that resides between the intermediate relaystation and the ingress station.
 20. The intermediate relay station ofclaim 17 wherein to determine the intermediate relay station deliverydeadline for the packet data unit, the control system is further adaptedto: determine propagation information bearing on how long it may takethe packet data unit to be delivered to the egress station from theintermediate relay station; and calculate the intermediate relay stationdelivery deadline based on the propagation information and the egressstation delivery deadline.
 21. The intermediate relay station of claim20 wherein the intermediate relay station delivery time is calculated atleast in part by subtracting the propagation information from the egressstation delivery deadline.
 22. The intermediate relay station of claim17 wherein the intermediate relay station delivery deadline correspondsto a time.
 23. The intermediate relay station of claim 17 wherein theintermediate relay station delivery deadline corresponds to a frame fortransmission.
 24. The intermediate relay station of claim 17 wherein theingress station is a base station and the egress station is an accessrelay station supporting wireless communications with at least one userterminal, which is party to the at least one service flow.
 25. Theintermediate relay station of claim 17 wherein the egress station is abase station and the ingress station is an access relay stationsupporting wireless communications with at least one user terminal,which is party to the at least one service flow.
 26. The intermediaterelay station of claim 17 wherein when multiple packet data units of theplurality of packet data units have the same intermediate stationdelivery deadline, quality of service class information associated withthe multiple packet data units is used to control an order in which themultiple packet data units are delivered toward the egress station. 27.The intermediate relay station of claim 17 wherein the control system isfurther adapted to: determine propagation metrics bearing on at leastone link between the intermediate relay station and the egress station;and deliver information bearing on the propagation metrics toward theingress station.
 28. The intermediate relay station of claim 27 whereinthe propagation metrics for the at least one link are delivered towardthe ingress station in a log, which has a different field for thepropagation metrics for each link being reported.
 29. The intermediaterelay station of claim 17 wherein each of the plurality of packet dataunits comprises quality of service (QoS) class information bearing on aQoS class for the packet data unit and is delivered with the QoS classinformation and the egress station delivery deadline toward the egressstation on or before the intermediate relay station delivery deadline.30. A method for operating an ingress station that resides in a wirelesscommunication access path in a wireless communication environment,wherein a tunnel is established between the ingress station and anegress station through at least one intermediate relay station along thewireless communication access path, the method comprising: receiving aplurality of packet data units associated with at least one service flowthat is supported by the tunnel; for each packet data unit of theplurality of packet data units: determining an egress station deliverydeadline on or before which the egress station should deliver the packetdata unit toward a destination of the packet data unit; providing theegress station delivery deadline with the packet data unit; anddelivering the packet data unit with the egress station deliverydeadline to an intermediate relay station via the tunnel.
 31. The methodof claim 30 further comprising: identifying quality of service (QoS)class information bearing on a QoS class for the packet data unit; andproviding the egress station delivery deadline with the packet dataunit, wherein the packet data unit is delivered with the QoS informationand the egress station delivery deadline to the intermediate relaystation via the tunnel.
 32. The method of claim 30 further comprisingdetermining an ingress station delivery deadline for the packet dataunit on or before which the ingress station should deliver the packetdata unit to the intermediate relay station to ensure the packet dataunit reaches the egress station in sufficient time to be deliveredtoward the destination of the packet data unit by the egress stationdelivery deadline, and wherein the packet data unit is delivered to theintermediate relay station on or before the ingress station deliverytime.